LC-ICP-MS has important advantages for speciation analysis:
Complex chromatograms are reduced to simple "elementograms"
Quantification of even unknown element species is possible with respect to the detected element due to compound independent sensitivity without the necessity of having standards.
However the hard ionization and atomization power of the plasma source also has some drawbacks:
All molecular information is lost
Species characterization is limited to chromatographic retention times
Looking more closely onto the hyphenated system, some details have to be discussed:
contamination with metallic compounds arising from the chromatographic system (pump, valve, tubing) or the stationary and mobile phase,
dispersion effects, that means the influence on the sample introduction system on the separation power of the chromatographic system,
plasma solvent load effects, that means the influence on the mobile phase on the stability and ionization power of the inductively coupled plasma.
Plasma solvent load effects limit the free choice of the mobile phase, since now the mobile phase has to be selected both with respect to the separation task but also with respect to the degree of tolerance by the ICP. Tolerance by the ICP can be enhanced by reducing the flow-rate, which can be achieved by reducing the size-factor of the HPLC system from standard to micro-HPLC or even nano-HPLC. Tolerance of the ICP with nano-liter flow rates is so high that nearly any solvent can be introduced with total consumption nebulizers.
On the other hand, the negative influence of dead-volumes and other poor design factors on the chromatographic separation power is the more pronounced the smaller the flow rate of the system is. Therefore, especially careful design considerations are necessary for nano-HPLC coupling while standard system are less critical.
With respect to the type of MS detection system, one has to consider the transient character of the chromatogtaphic signals. Depending on the number of simultaneous channels that have to be monitored (only one in the simple case of a single element speciation), systems that can either simultaneously collect data on different channels or can do fast sequential measurements will have advantages.